SAW controlled transversal filter - has charge transfer effected by acoustically excitable blade mounted at end of piezoelectric transducer connected to generator

摘要

The transversal charge transfer filter comprises a semiconductor substrate (10) e.g. p-type silicon coated with a series of parallel electrode strips (14) some of which are gapped with the two portions connected to respective terminal electrodes running the length of the substrate and coupled to respective inputs of a differential amplifier (20). The series is proceded by a charge injection diode (16) and followed by a charge collector diode (18). Control of charge transfer is effected by a leaf (22) of e.g. niobium and lithium, which can propagate a surface acoustic wave, the leaf having a piezoelectric transducer (24) at one end connected to an a.c. generator (26) and a shock absorber (28) at the other. The leaf is located on the substrate electrodes so that propagation of a surface wave ensures charge displacement in the substrate.